Generally, all turtles and tortoises are slow when walking on land. The average turtle can walk at a speed of 3 to 4 mph, but they can swim at a pace of 10 to 12 mph. Turtles are also typically faster than tortoises, who average 0.13 to 0.3 mph on land. While they may be slow walkers, turtles and tortoises are powerful swimmers. The green sea turtle, for instance, can swim at a speed of 20 mph.